In the endoscopic examination or surgery of a joint and in many other styles of examination, surgery, and treatment it is necessary to pump a physiological liquid, typically a sterile saline solution, into one location of the joint or other area being worked on and to evacuate it at an adjacent location. This is particularly the case in the arthroscopic examination of the knee in which an image of the joint is transmitted to a video display by a fiber-optic cable carried on the tool inserted into the knee joint. This technique is used also to inspect the meniscus, knee ligaments, the sinoviale of cartilage, and the socket of the femur and tibia as well as to operate on certain conditions such as a ruptured miniscus, a folded synovial, a bone chip, or just to rinse out the knee joint.
With such a surgical tool it is necessary not only to control the pressure (force/unit of area) of the liquid being injected into the joint, but also to be able to control its flow rate (volume/unit of time). During a simple examination where no blood or excised particles are freed flow rate is not critical but when doing an endoscopic resection with the concomitant generation of unwanted particles it is necessary to be able to increase the flow rate and thus maintain visibility while ridding the joint of unnecessary material. This is normally done by using a special-duty auxiliary conduit which can be moved by the doctor to a location where material is to be aspirated.
Thus the liquid-feed apparatus normally comprises a main suction conduit that is implanted without possibility of substantial movement other than removal at the top of the joint, a feed conduit that is connected to the pump output and that is implanted in the knee opposite the main suction conduit, and an auxiliary suction conduit that passes through the tool and opens adjacent its reversible rotary blade. Thus material cut off and ground up by the endoscopic tool can be aspirated right at the site it is cut from.
As a result in order to control this device it is necessary to provide a switch for reversing the motor driving the blade, a switch that can turn on or off the motor, one that can raise and lower the suction and/or feed pump rate, and one that can select between which one of the suction conduits is connected to the pump intake. This makes it possible to switch on the tool-mounted suction line when using the tool, and also allows the device to be used without operation of the tool, simply for examination and/or aspiration purposes. Typically these functions are controlled by foot pedals to leave the hands of the surgeon free.
In general the tools of this type in current use are both excessively complex to operate and difficult to control accurately.